I'd have seconded the Rattle/BPO/EMI M9th had they issued it (alongside the CD) in DVD-R format with improved sound.
Other than that, I don't have particular affinity for any of the new Mahler releases, but will mention that I rather liked Zinman's M2nd and M3rd.
The Gergiev/LSO/LSO M3rd is another highlight of 2008 I'd like to point out.
To me, this was a year that led me to revisit Shostakovich through some excellent recordings; Wigglesworth/NRPO/BIS 8th & 13th, Haitink/CSO/CSO 4th, and finally Schwarz/SSO/Artek 8th. The power of Shosy's music never diminishes next to Mahler's. That's what I realized.
John,